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In my experience both DAPI and Hoechst 33258 stain live cells if applied at
a sufficiently high concentration and time of incubation. At 1 uM during 30
minutes at room temperature these dyes show only marginal staining in the
cell types I used (human fibroblasts and lymphoid cell lines). There may be
cell types which respond in a dramatically different way, however.
For live/dead discrimination I would recommend propidium iodide or the new
SYTOX Green stain from Molecular Probes, Inc. Both dyes are 488 nm
excitable, but the SYTOX Green dye gives a much higher fluorescence
enhancement upon binding to DNA.
To resolve live cells on the basis of their ploidy level only Hoechst 33342
is available right now. It should be noted, however, that this dye is
stongly biased toward AT base pairs. That means that the differences in
fluorescence you may pick up could very well reflect differences in relative
AT content rather than the total amount of DNA in your cells.
I hope this will help you in chosing the best dye for your appplication.
Martin Poot
martin@probes.mhs.compuserve.com
Molecular Probes, Inc.
P.O. Box 22010
Eugene OR 97402
Tel : (503) 465 - 8300
FAX : (503) 344 - 6504
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